This invention relates to electrostatographic xerographic type reproduction machines, and more particularly, to an improved developing system for such machines.
In electrostatic type copying or reproducing machines, development of the electrostatic images being processed is today generally effected through the use of one or more magnetic brush rolls. To enhance development, the magnetic brush roll or rolls may have a voltage potential applied thereto to facilitate pickup of developing material by the roll or rolls and to aid in controlling the flow of toner from the magnetic brush roll or rolls to the electrostatic latent image.
In this connection, U.S. Pat. No. 3,805,739 to Ronald F. Feldeisen et al provides for selection of a voltage potential for biasing purposes above or below the normal biasing potential in response to whether the original being copies is dark or light. However, the aforedescribed makes no provision permitting the voltage selection to be infinitely varied by the operator when making copies thus giving the operator extremely fine control over the density of the copies produced.
It is therefore a principal object of the present invention to provide a new and improved electrostatic reproduction machine.
It is a further object of the present invention to provide an improved developing system for electrostatic type copiers.
It is an object of the present invention to provide an improved electrostatic developing system having control means to permit the image density to be infinitely varied.
It is an object of the present invention to provide a development control allowing voltage bias levels on the magnetic brush developing roll or rolls to be infinitely varied.
It is an object of the present invention to provide a magnetic brush developer having a biasing control effective to allow either a preselected biasing voltage or infinitely variable biasing voltages to be applied by the operator.
This invention relates to a reproduction machine for producing copies having at least one magnetic brush developing roll for developing electrostatic latent images processed by the reproduction machine together with voltage means for applying a biasing voltage to the developing roll to enhance development, in which the improvement comprises, control means for varying the biasing voltage over an infinitely variable range.